1. Field of the Invention
The present invention relates generally to a fluid-filled elastic mount adapted to dampen or isolate vibrations applied thereto, based on flow of a non-compressible fluid contained therein, and more particularly to such a fluid-filled elastic mount which exhibits excellent fluid-tightness of a fluid chamber filled with the fluid, assuring a high degree of durability. The invention is also concerned with a method of manufacturing such a fluid-filled elastic mount as described above.
2. Discussion of the Prior Art
An elastic mount is known as a vibration damping member interposed between two members of a vibration system, for flexibly connecting these two members. As one type of the elastic mount, there is known a so-called fluid-filled elastic mount as disclosed in laid-open Publication No. 57-9340 of unexamined Japanese Patent Application, which has a pressure-receiving chamber and a variable-volume equilibrium chamber which are filled with a suitable non-compressible fluid. The pressure-receiving chamber is partially defined by an elastic body for flexibly connecting two support structures fixed to the above two members, and a pressure of the fluid in this chamber changes due to elastic deformation of the elastic body upon application of vibrations to the mount. The equilibrium chamber is partially defined by a flexible diaphragm, which allows a volumetric change of this chamber due to its elastic deformation, so as to avoid a pressure change of the fluid therein. These pressure-receiving and equilibrium chambers communicate with each other through an orifice passage. This fluid-filled elastic mount is capable of providing an excellent vibration damping effect which cannot be obtained by the elasticity of the elastic body alone, based on resonance of the fluid flowing through the orifice passage. Thus, the fluid-filled elastic mount of the above type is favorably used as an engine mount for a motor vehicle, for example.
In manufacturing the fluid-filled elastic mount as disclosed in the above-identified publication, a cylindrical connecting member is secured by vulcanization to an outer circumferential surface of the elastic body, and an opening of the connecting member is fluid-tightly closed by an appropriate closure member, whereby a fluid chamber is formed between the elastic body and the closure member. This arrangement facilitates the formation of the fluid chamber (i.e., the pressure-receiving and equilibrium chambers), and the filling of the fluid chamber with the fluid. To assure sufficient fluid-tightness of the fluid chamber formed in the elastic mount, it is required to provide a high degree of fluid-tight seal between relevant engaging portions of the closure member and the connecting member upon assembling thereof.
In the known fluid-filled elastic mount, the closure member and the connecting member are assembled together by a caulking technique. More specifically, an open end portion or caulking portion of one of these closure and connecting members is caulked against an open end portion of the other member, so that the open end portion of the other member is gripped by the caulking portion of the above-indicated one member, in the axial direction of the mount. In this manner, the closure member is assembled with the connecting member, with a sealing rubber layer sandwiched between the engaging portions of these members, thereby assuring fluid-tight sealing between these portions.
In the fluid-filled elastic mount with the connecting and closure members assembled by the caulking technique, the vibrations are applied between the connecting and closure members, in the axial direction in which the gripping force of the caulking portion of the above-indicated one member is applied to the end portion of the other member. Therefore, the caulking engagement between the connecting and closure members may be gradually loosened due to the applied vibrations, resulting in reduction in the gripping force of the caulking portion. Since the elastic mount of the above type relies on the gripping force of the caulking portion for giving fluid-tight sealing between the connecting and closure members, the reduced gripping force tends to result in deterioration in fluid-tightness of the fluid chamber, causing a problem of leakage of the fluid from the fluid chamber. Thus, it is difficult for the known fluid-filled elastic mount to have a sufficiently high degree of durability.